Consider the following statements:
(A) Hertz first produced and detected electromagnetic waves of wavelength of a few metres in the laboratory.
(B) Maxwell’s equations, together with the Lorentz force formula, express all the basic laws of electromagnetism.
(C) Charges moving with uniform velocity are sources of electromagnetic waves.
(D) An oscillating electric dipole is a basic source of electromagnetic waves.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (D) only
(A) Hertz first produced and detected electromagnetic waves of wavelength of a few metres in the laboratory. — True. Hertz did this in 1887. It confirmed a basic prediction of Maxwell’s equations.
(B) Maxwell’s equations, together with the Lorentz force formula, express all the basic laws of electromagnetism. — True. Maxwell’s equations give the fields from charges and currents. The Lorentz force formula gives the force of these fields on a charge.
(C) Charges moving with uniform velocity are sources of electromagnetic waves. — False. A charge in uniform motion is a steady current. Its magnetic field does not change with time, so it does not radiate. Only accelerated charges radiate electromagnetic waves.
(D) An oscillating electric dipole is a basic source of electromagnetic waves. — True. The charges of an oscillating dipole move to and fro, so they keep accelerating. Accelerated charges radiate electromagnetic waves.
NCERT (2026-27):
Summary – “3. Electromagnetic waves with wavelength of the order of a few metres were first produced and detected in the laboratory by Hertz in 1887. …”
Introduction – “… Together with the Lorentz force formula (Chapter 4), they mathematically express all the basic laws of electromagnetism.”
Sources of electromagnetic waves – “How are electromagnetic waves produced? Neither stationary charges nor charges in uniform motion (steady currents) can be sources of electromagnetic waves. …”
Summary – “… An electric charge oscillating harmonically with frequency ν, produces electromagnetic waves of the same frequency ν. An electric dipole is a basic source of electromagnetic waves.”